The effect of galacto-oligosaccharides on growth and viability of probiotic bacteria in fermented whey based bevereage

Abstract

Galacto-oligosaccharides (GOS) are produced from milk lactose during transgalactosylation reaction using  -galactosidase. Depending on reaction condition,  -galactosidase can, also, hydrolyse lactose, in order to make beverage more suitable for lactose intolerant individuals. GOAL: The aim of this study was to evaluate the prebiotic effect of the GOS, inulin and lactulose on growth and viability of probiotic bacteria in fermented whey based beverage. METHOD: Mixture of cow’s milk and whey (30%:70%) was subjected to transgalactosylation reaction using commercial β-galactosidase isolated from Aspergillus oryzae (0,5 mg/l). Before fermentation, samples were heat treated 15 minutes at 90 0C and after cooling on fermentation temperature (42 0C), samples were inoculated with lyophilized ABY-6 starter cultures. After fermentation and during refrigerated storage (28 days), samples were analyzed by measuring: pH value, titratable acidity, carbohydrate concentrations, total number of probiotic bacteria cells and syneresis. RESULT: Higher concentration of galacto-oligosaccharides was reached after 1,5h since, in the further course of transgalactosylation reaction, some amount of galacto-oligosaccharides were hydrolyzed to glucose and galactose. Slightly shorter fermentation time and higher viable cell number of probiotic bacteria were noticed in fermented whey based beverages with galacto-oligosaccharides than in beverages with inulin, lactulose and without prebiotics. During 28 days storage, changes in pH value and titratable acidity were not different significantly among beverages. Beverages with galacto-oligosaccharides had less syneresis and curd showed a better water holding capacity than other tested samples. After 28 days of storage, presence of different prebiotics in samples did not significantly influenced total number of probiotic bacteria cells (Lactobacillus acidophilus and Bifidobacterium bifidum), but in samples with galacto-oligosaccharides were noticed slightly higher content of Bifidobacterium bifidum. CONCLUSION: Regular use of fermented dairy beverages with galacto-oligosaccharides and probiotic bacteria, could favorably affect human health, modulating the composition of the colonic microflora.